This invention relates to an electric circuit interrupter of the puffer type and, more particularly, to a circuit interrupter of this type which comprises a floating piston that is magnetically driven during a circuit-interrupting operation to pressurize fluid that is subsequently directed into the arcing zone to aid in arc-extinction.
Circuit interrupters of the puffer type utilize a cooperating cylinder and piston as a means for compressing gas which is subsequently directed into the arcing zone to aid in arc-extinction. In one typical puffer-type circuit interrupter design, the cylinder is coupled to the usual operating rod for the movable contact of the circuit interrupter, and relative movement between the cylinder and piston is effected by movement of the operating rod. It has been recognized that such designs are usually rather slow in effecting circuit interruption of high currents because a relatively large travel of the operating rod is usually required before the pressure in the cylinder is increased to the high value desired for effective high-current circuit interruption.
To overcome this problem it has been proposed to make the piston a floating piston provided with its own driving means for accelerating the gas-compression operation. In U.S. Pat. No. 3,331,935--Milianowicz, this separate driving means compises a latched compression spring which is suitably released early in the interrupting operation. In U.S. Pat. No. 3,721,786--Yoshioka (FIG. 6) the separate driving means comprises an electromagnet having an armature coupled to the floating piston and magnetically driven by a repulsion force when the coil of the electro-magnet is energized.
A disadvantage of the latter circuit interrupter is that the force on the floating piston depends upon the position of the piston and after an initial increase drops rapidly as the armature moves away from the coil of the electromagnet.